(a) The Department with reference to State highways under its jurisdiction, and local authorities with reference to other highways under their jurisdiction, may designate through highways and erect stop signs or yield signs at specified entrances thereto, or may designate any intersection as a stop intersection or as a yield intersection and erect stop signs or yield signs at one or more entrances to such intersection. Designation of through highways and stop or yield intersections and the erection of stop signs or yield signs on township or road district roads are subject to the written approval of the county engineer or superintendent of highways.
     (b) Every stop sign and yield sign shall conform to the State Manual and Specifications and shall be located as near as practicable to the nearest line of the crosswalk on the near side of the intersection or, if there is no crosswalk, then as close as practicable to the nearest line of the intersecting roadway.
     (c) The Department may in its discretion and when traffic conditions warrant such action give preference to traffic upon any of the State highways under its jurisdiction over traffic crossing or entering such highway by erecting appropriate traffic control devices.